The roles of metabolism, immune processes, DNA repair, and other factors related to susceptibility to transplacental carcinoigenesis in rodents and primates are investigated, with emphasis on nitrosamine and aromatic hydrocarbon carcinogens and utilizing both whole animal and in vitro culture techniques. BIBLIOGRAPHIC REFERENCES: Rice, J.M.: Environmental Factors: Chemicals. In Brent, R.L. and Harris, M. (Eds.): Prevention of Embryonic, Fetal, and Perinatal Disease. DHEW Publ. No. (NIH) 76-853. Wash., D.C., U.S. Govt. Print. Off., 1976, 163-177 pp. Levy, B., London, W., Fucillo, D.A., Baron, S., and Rice, J.: Prophylactic control of simian hemorrhagic fever in monkeys by an interferon inducer, polyrioinosinic polyribocytidylic acid-poly-L-lysine. J. Infect. Dis. 133 Suppl: A256-A259, 1976.